Its plot follows the Union Army's 35th Maine Volunteer Infantry and 44th New York Light Artillery as they board a transport ship, the Ogunquit, in City Point, Virginia, on January 2, 1865.

They quickly find friends and enemies in this new world where past civilizations from Earth were transported including feudal Russians, ancient Romans and Carthaginians, Zulus and others.

In book two, Keane and his men prepare for the coming of the Tugars, the northernmost group of Horde aliens.

They are thrown into an intricate network of political feuds where the boyar, Ivor, struggles against the church for power.

Keane allows for a vote to either stay and fight with Rus or to leave and try and mass strength elsewhere while avoiding the horde.

The church's prelate, Rasnar, convinces Ivor to attack Keane and steal the guns on the night of the vote.

The peasants revolt and are led particularly by one man, Kalencka (Kal), who befriends the Maine men and becomes an interpreter for Ivor.

Keane manages to come to the aid of peasants in time, and shortly after Rasnar and Ivor kill each other.

Though their faces are somewhat apelike and in other ways resemble the wolfman, their bodies are Herculean in build and of handsome appearance.

Tugar society is ruled by males with their females taking no significant social, political, or military role, quite unlike human nomads.

The Tugars rely on humans for all the food and manufactured goods to maintain their nomadic way of life.

Most Tugars think that humans are simply inferior and have no souls, and cannot imagine that they would revolt rather than accept the status quo.

Once the Tugars destroyed the advanced aliens by force of numbers they refused to copy their weapons and threw them into the sea.

The Maine men, being of many skills and crafts, set about trying to create a modern industry in only a year or so.

A Tugar agent, called the "Namer of Time" is the first alien leader to show up, with his escort and some Rus "pets" who have not seen their homes for twenty years.

The Qar Qarth of the Tugars, Muzta, faces opposition within his horde so he does not listen to the advice of his advisor Qubata to draw out the attack and starve the Yankees into submission.

At the last minute, Keane's protegee, Vincent Hawthorne, commandeers their scouting balloon and daringly flies it to the dam the men constructed.